Defibrillators are used to treat Sudden Cardiac Arrest by applying a defibrillating shock to the heart of a cardiac arrest patient via electrodes placed on the chest of the patient. An electrocardiogram (ECG) signal of a patient experiencing cardiac arrest, properly measured and analyzed, provides an indication of whether the patient's heart is exhibiting a shockable rhythm or a non-shockable rhythm. A shockable rhythm refers to an aberrant ECG signal where a defibrillation shock is advised for restoration of a normal heartbeat, while a non-shockable rhythm refers to an ECG signal where a defibrillation shock is not advised. Ventricular fibrillation, for example, is a shockable rhythm, while asystole or pulseless electrical activity is an example of a non-shockable rhythm. Defibrillators are also capable of treating other dysrhythmias (irregular heartbeats), such as atrial fibrillation, bradycardia, and tachycardia. An ECG signal may be obtained through electrodes placed on the chest of the patient, and the defibrillating or cardioverting shock may be applied through the same electrodes.
During resuscitation, treatment protocols recommended by the American Heart Association and European Resuscitation Council advise for the rescuer to regularly check the patient's pulse or to evaluate the patient for signs of circulation. If no pulse or sign of circulation is present, the rescuer may be often instructed to perform cardio pulmonary resuscitation (CPR) on the victim for an appropriate period of time between shock analyses, where CPR involves applying both chest compressions and ventilations to the victim. Chest compressions and/or ventilations may be monitored during the course of CPR, for example, through systems and technologies that incorporate real-time CPR feedback (e.g., REAL CPR HELP® systems available from ZOLL® Medical Corporation) and which may implement resuscitation assemblies (e.g., CPR-D-PADZ® resuscitation assemblies, CPR STAT-PADZ® resuscitation assemblies, and OneStep CPR resuscitation assemblies available from ZOLL® Medical Corporation) having a sensor for obtaining chest compression related information for manual CPR providers. For example, ZOLL's CPR-D-PADZ® resuscitation assemblies and CPR STAT-PADZ® resuscitation assemblies include a pair of electrode pads and a single chest compression sensor.